<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        table {
            margin: 0 auto;
            border: 1px solid green;
            width: 50%;
        }

        table td {
            border: 1px solid blue;
        }
    </style>
</head>
<body>
<table>
    <tr>
        <td>11</td>
        <td>12</td>
        <td>13</td>
        <td>14</td>
    </tr>
    <tr>
        <td>21</td>
        <td>22</td>
        <td>23</td>
        <td>24</td>
    </tr>
    <tr>
        <td>31</td>
        <td>32</td>
        <td>33</td>
        <td>34</td>
    </tr>
</table>
</body>
</html>